AMENDMENT NO. 4

                                       TO

                           LOAN AND SECURITY AGREEMENT



            AMENDMENT NO. 4 TO LOAN AND SECURITY AGREEMENT  ("AMENDMENT")  dated
as of December  31,  1999,  is among KMC TELECOM  INC.,  a Delaware  corporation
("KMC"), KMC TELECOM II, INC., a Delaware corporation ("KMC II"), KMC TELECOM OF
VIRGINIA, INC., a Virginia public service company ("KMC VIRGINIA"),  KMC TELECOM
LEASING I LLC, a Delaware limited  liability  company ("LEASING I"), KMC TELECOM
LEASING II LLC, a Delaware limited liability company ("LEASING II"; KMC, KMC II,
KMC Virginia,  Leasing I and Leasing II being hereinafter  collectively referred
to hereinafter as the "BORROWERS"), the financial institutions from time to time
parties thereto (the  "LENDERS"),  FIRST UNION NATIONAL BANK, as  administrative
agent for the Lenders (the "AGENT") and NEWCOURT  COMMERCIAL FINANCE CORPORATION
(f/k/a AT&T  COMMERCIAL  FINANCE  CORPORATION),  an  affiliate of The CIT Group,
Inc., as collateral  agent for the Lenders (the  "COLLATERAL  AGENT";  the Agent
together with the Collateral Agent being referred to as the "AGENTS").

            WHEREAS,  the  Borrowers,  the Agents and the Lenders are parties to
that  certain  Loan and  Security  Agreement  (the "LOAN  AGREEMENT";  undefined
capitalized  terms used herein shall have the meanings  assigned  thereto in the
Loan  Agreement)  dated as of December  22, 1998,  as amended by Amendment  No.1
thereto  dated as of March 3, 1999,  Amendment  No. 2 thereto dated as of August
13, 1999,  and Waiver and  Amendment No. 3 thereto dated as of October 29, 1999,
pursuant to which the  Lenders  have  agreed to make  certain  "Loans" and other
financial accommodations to the Borrowers; and

            WHEREAS,  the  Borrowers  have  requested  that the  Agents  and the
Lenders amend the Loan Agreement in the manner set forth herein,  and the Agents
and the Lenders have agreed to such request;

            NOW,  THEREFORE,  in  consideration of the premises set forth above,
and for other good and valuable  consideration,  the receipt and  sufficiency of
which are hereby acknowledged,  the Borrowers,  the Agents and the Lenders agree
as follows:

            1. AMENDMENT TO THE LOAN  AGREEMENT.  Effective as of the date first
above  written and subject to the  execution  of this  Amendment  by the parties
hereto, the Loan Agreement shall be and hereby is amended as follows:

            1.1 SECTION  7.01(b) is hereby amended to add the following  proviso
thereto: ---------------

            "PROVIDED,  HOWEVER,  that as of the last day of each fiscal quarter
occurring on or after December 31, 1999, the Borrowers shall on a combined basis
have revenues at least equal to the amount set forth below for such date:




FISCAL QUARTER ENDING                     MINIMUM REVENUES

December 31, 1999                         $18,000,000
March 31, 2000                            $23,821,000
June 30, 2000                             $31,338,000
September 30, 2000                        $37,803,000
December 31, 2000                         $44,482,000
March 31, 2001                            $54,678,000"

            1.2  SECTION  7.01(c)(i)  is hereby  amended to delete  the  proviso
thereto and to substitute the following proviso therefor:

            "PROVIDED,  HOWEVER,  that as of the last day of each fiscal quarter
occurring on or after December 31, 1999 through and including December 31, 2000,
the  Borrowers  shall not permit the EBITDA  losses for all the  Borrowers  on a
combined basis for the two fiscal  quarters then ending to exceed the amount set
forth below for such date:

FISCAL QUARTER ENDING                     EBITDA LOSSES

December 31, 1999                         ($50,400,000)
March 31, 2000                            ($38,700,000)
June 30, 2000                             ($25,001,000)
September 30, 2000                        ($13,823,000)
December 31, 2000                         ($4,157,000)"

            1.3  SECTION  7.01(c)(ii)  shall  be  deleted  in its  entirety  and
replaced with the following new SECTION 7.01(c)(ii):

            "As of the last day of the fiscal quarter ending March 31, 2001, the
Borrowers  shall not permit EBITDA for all the Borrowers on a combined basis for
the two fiscal quarters then ending to be less than $1,688,000."


            2. CONDITIONS PRECEDENT. This Amendment shall become effective as of
the date above written,  if, and only if, the Agents have received duly executed
originals of this Amendment from the  Borrowers,  the Requisite  Lenders and the
Agents on or prior to January __, 2000.

            3.  REPRESENTATIONS  AND WARRANTIES OF THE BORROWERS.  The Borrowers
hereby represent and warrant as follows:

            (a)  This  Amendment  and the Loan  Agreement,  as  amended  hereby,
constitute  legal,  valid  and  binding  obligations  of the  Borrowers  and are
enforceable against the Borrowers in accordance with their terms.

            (b) Upon the  effectiveness of this Amendment,  the Borrowers hereby
reaffirm all representations  and warranties made in the Loan Agreement,  and to
the extent the same are not amended hereby,  agree that all such representations
and warranties shall be deemed to have been remade as of the date of delivery of


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this  Amendment,  unless  and to the  extent  that any such  representation  and
warranty  is stated to relate  solely to an  earlier  date,  in which  case such
representation and warranty shall be true and correct as of such earlier date.

            (c)  As of  the  date  hereof,  and  after  giving  effect  to  this
Amendment,  each  Borrower  shall  be in  compliance  with  all  the  terms  and
provisions set forth in the Loan Agreement, as amended hereby, on its part to be
observed or  performed,  and no Event of Default or Default  shall have occurred
and be continuing.

            4. REFERENCE TO AND EFFECT ON THE LOAN AGREEMENT.

            (a) Upon the  effectiveness  of  Section 1 hereof,  on and after the
date  hereof,  each  reference in the Loan  Agreement to "this Loan  Agreement,"
"hereunder,"  "hereof,"  "herein"  or words of like  import  shall mean and be a
reference to the Loan  Agreement as amended  hereby,  and each  reference to the
Loan Agreement in any other document,  instrument or agreement shall mean and be
a reference to the Loan Agreement as modified hereby.

            (b) The Loan Agreement,  as amended hereby, and all other documents,
instruments and agreements  executed and/or  delivered in connection  therewith,
shall remain in full force and effect, and are hereby ratified and confirmed.

            (c) Except as expressly provided herein, the execution, delivery and
effectiveness  of this  Amendment  shall not  operate  as a waiver of any right,
power or remedy of the Agents or the  Lenders,  nor  constitute  a waiver of any
provision  of  the  Loan  Agreement  or any  other  documents,  instruments  and
agreements executed and/or delivered in connection therewith.

            5. GOVERNING LAW. THIS AMENDMENT  SHALL BE GOVERNED BY AND CONSTRUED
IN  ACCORDANCE  WITH THE OTHER  REMAINING  TERMS OF THE LOAN  AGREEMENT  AND THE
INTERNAL  LAWS (AS OPPOSED TO CONFLICT  OF LAW  PROVISIONS)  OF THE STATE OF NEW
YORK.

            6.  PARAGRAPH  HEADINGS.  The paragraph  headings  contained in this
Amendment  are and shall be  without  substance,  meaning or content of any kind
whatsoever and are not a part of the agreement among the parties thereto.

            7.  COUNTERPARTS.  This  Amendment  may be  executed  in one or more
counterparts,  each of  which  shall be  deemed  an  original,  but all of which
together shall constitute one and the same instrument.




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            IN WITNESS WHEREOF,  this Amendment has been duly executed as of the
day and year first above written.

THE BORROWERS:                     KMC TELECOM INC.

                                   KMC TELECOM II, INC.

                                   KMC TELECOM OF VIRGINIA, INC.

                                   In each case:

                                   By:  /s/
                                      -----------------------
                                   Name: James D. Grenfell
                                   Title:      CFO


                                   KMC TELECOM LEASING I LLC
                                   By:  KMC TELECOM INC., as its Sole Member


                                   By:  /s/
                                      -----------------------
                                   Name:  James D. Grenfell
                                   Title:      CFO


                                   KMC TELECOM LEASING I LLC
                                   By:  KMC TELECOM II, INC., as its Sole Member


                                   By:  /s/
                                      -----------------------
                                   Name: James D. Grenfell
                                   Title:      CFO





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                                   FIRST UNION NATIONAL BANK, as the
                                   Agent and as a Lender


                                   By:  /s/
                                      -------------------------
                                   Name: Elizabeth Elmore
                                   Title: Senior Vice President


                                   NEWCOURT  COMMERCIAL FINANCE  CORPORATION
                                   (f/k/a    AT&T     COMMERCIAL     FINANCE
                                   CORPORATION),  an  affiliate  of The  CIT
                                   Group,  Inc., as the Collateral Agent and
                                   as a Lender


                                   By:  /s/
                                      -------------------------
                                   Name: Michael Monahan
                                   Title: Vice President


                                   CANADIAN IMPERIAL BANK OF
                                   COMMERCE, as a Lender


                                   By:  /s/
                                      -------------------------
                                   Name: Tefta Chilaga
                                   Title: Executive Director, CIBC World
                                              Markets Corp. As Agent


                                   GENERAL ELECTRIC CAPITAL
                                   CORPORATION, as a Lender


                                   By:  /s/
                                      -------------------------
                                   Name: Mark F. Mylon
                                   Title: Manager-Operations


                                   BANKBOSTON, N.A., as a Lender


                                   By:  /s/
                                      --------------------------
                                   Name: Michael A. Ashton
                                   Title: Vice President





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                                   CREDIT SUISSE FIRST BOSTON, as a
                                   Lender

                                   By:  /s/
                                      --------------------------
                                   Name: Jeffery Ulmer
                                   Title: Vice President

                                   By:  /s/
                                      --------------------------
                                   Name: Douglas E. Maher
                                   Title: Vice President

                                   DRESDNER BANK AG NEW YORK AND
                                   GRAND CAYMAN BRANCHES, as a Lender

                                   By:  /s/
                                      --------------------------
                                   Name: John P. Fleseler
                                   Title: Senior Vice President

                                   By:  /s/
                                      --------------------------
                                   Name: Constance Loosemore
                                   Title: Assistant Vice President

                                   MORGAN STANLEY SENIOR FUNDING,
                                   INC., as a Lender

                                   By:  /s/
                                      --------------------------
                                   Name: T. Morgan Edwards II
                                   Title: Vice President

                                   By:
                                      --------------------------
                                   Name:
                                   Title:

                                   MORGAN STANLEY DEAN WITTER
                                   PRIME INCOME TRUST, as a Lender

                                   By:  /s/
                                      --------------------------
                                   Name: Shelia Finnely
                                   Title: Senior Vice President




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                                   UNION BANK OF CALIFORNIA, N.A., as a
                                   Lender


                                   By:  /s/
                                      --------------------------
                                   Name: Keith M. Wilson
                                   Title: Vice President

                                   KEYPORT LIFE INSURANCE COMPANY,
                                   as a Lender


                                   By:  /s/
                                      --------------------------
                                   Name: Brian W. Good
                                   Title: Vice President & Portfolio Manager

                                   STEIN ROE FLOATING RATE LIMITED
                                   LIABILITY COMPANY, as a Lender


                                   By:  /s/
                                      --------------------------
                                   Name: Brian W. Good
                                   Title: Vice President
                                          Stein Roe & Farnham Incorporated,
                                          Advisor to the Stein Roe Floating Rate
                                          Limited Liability Company





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                            REAFFIRMATION OF GUARANTY

            Reference  is hereby made to (i) that certain  Guaranty  dated as of
December 22, 1998 (as amended, restated, supplemented or otherwise modified from
time to  time,  the  "GUARANTY")  by KMC  Telecom  Holdings,  Inc.,  a  Delaware
corporation  (the  "GUARANTOR"),   in  favor  of  Newcourt   Commercial  Finance
Corporation  (formerly  known  as  AT&T  Commercial  Finance  Corporation),   an
affiliate of The CIT Group, Inc., as collateral agent for the ratable benefit of
the "Lenders" (defined below) (in such capacity,  the "COLLATERAL AGENT"),  (ii)
that  certain  Loan and  Security  Agreement  dated as of December  22, 1998 (as
amended,  restated,  supplemented  or otherwise  modified from time to time, the
"LOAN AGREEMENT") among KMC Telecom,  Inc., KMC Telecom II, Inc., KMC Telecom of
Virginia,  Inc., KMC Telecom  Leasing I LLC, KMC Telecom Leasing II LLC (each of
the foregoing being referred to collectively as the "BORROWERS"),  the financial
institutions  from time to time  parties  thereto (the  "Lenders"),  First Union
National Bank, as  administrative  agent for the Lenders (the "Agent"),  and the
Collateral  Agent,  and (iii) that certain  Amendment No. 4 to Loan and Security
Agreement dated as of December 31, 1999 (the  "AMENDMENT")  among the Borrowers,
the Lenders, the Agent and the Collateral Agent.

            The  Guarantor,   by  its  signature  below,   without  in  any  way
establishing a course of dealing,  hereby (i)  acknowledges  and consents to the
execution and delivery of the Amendment by the parties thereto, (ii) agrees that
the Amendment  shall not limit or diminish the  obligations  of the Guarantor to
guarantee all of the  "Obligations" of each Borrower under and as defined in the
Loan Agreement and such other amounts as are more specifically  described in the
Guaranty,  (iii) reaffirms all of its obligations  under the Guaranty,  and (iv)
agrees that the Guaranty remains in full force and effect and is hereby ratified
and confirmed.

            IN WITNESS WHEREOF,  this instrument has been executed and delivered
as of this 31st day of December, 1999.

                                     KMC TELECOM HOLDINGS, INC.


                                     By:  /s/
                                        --------------------------

                                     Name:   James D. Grenfell
                                     Title:  CFO, Executive Vice President and
                                             Secretary




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